The present invention relates generally to DNA delivery methods. More particularly, the invention relates to the use of recombinant adeno-associated virus (AAV) virions for delivery of a selected gene to muscle cells and tissue. The method provides for sustained, high-level expression of the delivered gene.
Gene delivery is a promising method for the treatment of acquired and inherited diseases. Muscle tissue is an appealing gene delivery target because it is readily accessible, well-differentiated and nondividing. Barr and Leiden (1991) Science 254:1507-1509. These properties are important in the selection of appropriate delivery strategies to achieve maximal gene transfer.
Several experimenters have demonstrated the ability to deliver genes to muscle cells with the subsequent systemic appearance of proteins encoded by the delivered genes. See, e.g., Wolff et al. (1990) Science 247:1465-1468; Acsadi et al. (1991) Nature 352:815-818; Barr and Leiden (1991) Science 254:1507-1509; Dhawan et al. (1991) Science 254:1509-1512; Wolff et al. (1992) Human Mol. Genet. 1:363-369; Eyal et al. (1993) Proc. Natl. Acad. Sci. USA 90:4523-4527; Davis et al. (1993) Hum. Gene Therapy 4:151-159.
Genes have been delivered to muscle by direct injection of plasmid DNA, such as described by Wolff et al. (1990) Science 247:1465-1468; Acsadi et al. (1991) Nature 352:815-818; Barr and Leiden (1991) Science 254:1507-1509. However, this mode of administration generally results in sustained but low levels of expression. Low but sustained expression levels may be effective in certain situations, such as for providing immunity.
Viral based systems have also been used for gene delivery to muscle. For example, human adenoviruses are double-stranded DNA viruses which enter cells by receptor-mediated endocytosis. These viruses have been considered well suited for gene transfer because they are easy to grow and manipulate and they exhibit a broad host range in vivo and in vitro. Adenoviruses are able to infect quiescent as well as replicating target cells and persist extrachromosomally, rather than integrating into the host genome.
Despite these advantages, adenovirus vectors suffer from several drawbacks which make them ineffective for long term gene therapy. In particular, adenovirus vectors express viral proteins that may elicit an immune response which may decrease the life of the transduced cell. This immune reaction may preclude subsequent treatments because of humoral and/or T cell responses. Furthermore, the adult muscle cell may lack the receptor which recognizes adenovirus vectors, precluding efficient transduction of this cell type using such vectors. Thus, attempts to use adenoviral vectors for the delivery of genes to muscle cells has resulted in poor and/or transitory expression. See, e.g., Quantin et al. (1992) Proc. Natl. Acad. Sci. USA 89:2581-2584; Acsadi et al. (1994) Hum. Mol. Genetics 3:579-584; Acsadi et al. (1994) Gene Therapy 1:338-340; Dai et al. (1995) Proc. Natl. Acad. Sci. USA 92:1401-1405; Descamps et al. (1995) Gene Therapy 2:411-417; Gilgenkrantz et al. (1995) Hum. Gene Therapy 6:1265-1274.
Gene therapy methods based upon surgical transplantation of myoblasts has also been attempted. See, e.g., International Publication no. WO 95/13376; Dhawan et al. (1991) Science 254:1509-1512; Wolff et al. (1992) Human Mol. Genet. 1:363-369; Dai et al. (1992) Proc. Natl. Acad. Sci. USA 89:10892-10895; Hamamori et al. (1994) Hum. Gene Therapy 5:1349-1356; Hamamori et al. (1995) J. Clin. Invest. 95:1808-1813; Blau and Springer (1995) New Eng. J. Med. 333:1204-1207; Leiden, J. M. (1995) New Eng. J. Ned. 333:871-872; Mendell et al. (1995) New Eng. J. Med. 333:832-838; and Blau and Springer (1995) New Eng. J. Med. 333:1554-1556. However, such methods require substantial tissue culture manipulation and surgical expertise, and, at best, show inconclusive efficacy in clinical trials. Thus, a simple and effective method of gene delivery to muscle, resulting in long-term expression of the delivered gene, would be desirable.
Recombinant vectors based on adeno-associated viruses (AAV) have been used for DNA delivery. AAV is a helper-dependent DNA parvovirus which belongs to the genus Dependovirus. AAV requires infection with an unrelated helper virus, such as adenovirus, a herpesvirus or vaccinia, in order for a productive infection to occur. The helper virus supplies accessory functions that are necessary for most steps in AAV replication. In the absence of such infection, AAV establishes a latent state by insertion of its genome into a host cell chromosome. Subsequent infection by a helper virus rescues the integrated copy which can then replicate to produce infectious viral progeny. AAV has a wide host range and is able to replicate in cells from any species so long as there is also a successful infection of such cells with a suitable helper virus. Thus, for example, human AAV will replicate in canine cells coinfected with a canine adenovirus. AAV has not been associated with any human or animal disease and does not appear to alter the biological properties of the host cell upon integration. For a review of AAV, see, e.g., Berns and Bohenzky (1987) Advances in Virus Research (Academic Press, Inc.) 32:243-307.
The AAV genome is composed of a linear, single-stranded DNA molecule which contains approximately 4681 bases (Berns and Bohenzky, supra). The genome includes inverted terminal repeats (ITRs) at each end which function in cis as origins of DNA replication and as packaging signals for the virus. The internal nonrepeated portion of the genome includes two large open reading frames, known as the AAV rep and cap regions, respectively. These regions code for the viral proteins involved in replication and packaging of the virion. For a detailed description of the AAV genome, see, e.g., Muzyczka, N. (1992) Current Topics in Microbiol. and Immunol. 158:97-129.
The construction of recombinant AAV (rAAV) virions has been described. See, e.g., U.S. Pat. Nos. 5,173,414 and 5,139,941; International Publication Numbers WO 92/01070 (published Jan. 23, 1992) and WO 93/03769 (published Mar. 4, 1993); Lebkowski et al. (1988) Molec. Cell. Biol. 8:3988-3996; Vincent et al. (1990) Vaccines 90 (Cold Spring Harbor Laboratory Press); Carter, B. J. (1992) Current Opinion in Biotechnology 3:533-539; Muzyczka, N. (1992) Current Topics in Microbiol. and Immunol. 158:97-129; and Kotin, R. M. (1994) Human Gene Therapy 5:793-801.
Recombinant AAV virion production generally involves cotransfection of a host cell with an AAV vector plasmid and a helper construct which provides AAV helper functions to complement functions missing from the AAV vector plasmid. In this manner, the host cell is capable of expressing the AAV proteins necessary for AAV replication and packaging. The AAV vector plasmid will include the DNA of interest flanked by AAV ITRs which provide for AAV replication and packaging functions. AAV helper functions can be provided via an AAV helper plasmid that includes the AAV rep and/or cap coding regions but which lacks the AAV ITRs. Accordingly, the helper plasmid can neither replicate nor package itself. The host cell is then infected with a helper virus to provide accessory functions, or with a vector which includes the necessary accessory functions. The helper virus transactivates the AAV promoters present on the helper plasmid that direct the transcription and translation of AAV rep and cap regions. Upon subsequent culture of the host cells, recombinant AAV virions harboring the DNA of interest, are produced.
Recombinant AAV virions have been shown to exhibit tropism for respiratory epithelial cells (Flotte et al. (1992) Am. J. Respir. Cell Mol. Biol. 7:349-356; Flotte et al. (1993) J. Biol. Chem. 268:3781-3790; Flotte et al. (1993) Proc. Natl. Acad. Sci. USA 90:10613-10617) and neurons of the central nervous system (Kaplitt et al. (1994) Nature Genetics 8:148-154). These cell types are well-differentiated, slowly-dividing or postmitotic. Flotte et al. (1993) Proc. Natl. Acad. Sci. USA 90:10613-10617; Kaplitt et al. (1994) Nature Genetics 8:148-154. The ability of AAV vectors to transduce nonproliferating cells (Podsakoff et al. (1994) J. Virol. 68:5656-5666; Russell et al. (1994) Proc. Natl. Acad. Sci. USA 91:8915-8919; Flotte et al. (1994) Am. J. Respir. Cell Mol. Biol. 11:517-521) along with the attributes of being inherently defective and nonpathogenic, place AAV in a unique position among gene therapy viral vectors.
Despite these advantages, the use of recombinant AAV virions to deliver genes to muscle cells in vivo has not heretofore been disclosed.
Accordingly, the present invention is based on the surprising and unexpected discovery that recombinant AAV (rAAV) virions provide for efficient delivery of genes and sustained production of therapeutic proteins in various muscle cell types. The invention allows for in vivo secretion of the therapeutic protein from transduced muscle cells such that systemic delivery is achieved. These results are seen with both in vivo and in vitro modes of DNA delivery. Hence, rAAV virions allow delivery of DNA directly to muscle tissue. The ability to deliver and express genes in muscle cells, as well as to provide for secretion of the produced protein from transduced cells, allows the use of gene therapy approaches to treat and/or prevent a wide variety of disorders.
Furthermore, the ability to deliver DNA to muscle cells by intramuscular administration in vivo provides a more efficient and convenient method of gene transfer.
Thus, in one embodiment, the invention relates to a method of delivering a selected gene to a muscle cell or tissue. The method comprises:
(a) providing a recombinant AAV virion which comprises an AAV vector, the AAV vector comprising the selected gene operably linked to control elements capable of directing the in vivo transcription and translation of the selected gene; and
(b) introducing the recombinant AAV virion into the muscle cell or tissue.
In particularly preferred embodiments, the selected gene encodes a therapeutic protein, such as erythropoietin.
In another embodiment, the invention is directed to a muscle cell or tissue transduced with a recombinant AAV virion which comprises an AAV vector, the AAV vector comprising a selected gene operably linked to control elements capable of directing the in vivo transcription and translation of the selected gene.
In still further embodiments, the invention is directed to a method of treating an acquired or inherited disease in a mammalian subject comprising introducing into a muscle cell or tissue of the subject, in vivo, a therapeutically effective amount of a pharmaceutical composition which comprises (a) a pharmaceutically acceptable excipient; and (b) recombinant AAV virions. The recombinant AAV virions comprise an AAV vector, the AAV vector comprising a selected gene operably linked to control elements capable of directing the transcription and translation of the selected gene when present in the subject.
In yet another embodiment, the invention is directed to a method of treating an acquired or inherited disease in a mammalian subject comprising:
(a) introducing a recombinant AAV virion into a muscle cell or tissue in vitro to produce a transduced muscle cell. The recombinant AAV virion comprises an AAV vector, the AAV vector comprising a selected gene operably linked to control elements capable of directing the transcription and translation of the selected gene when present in the subject; and
(b) administering to the subject a therapeutically effective amount of a composition comprising a pharmaceutically acceptable excipient and the transduced muscle cells from step (a).
In a further embodiment, the invention relates to a method for delivering a therapeutically effective amount of a protein systemically to a mammalian subject comprising introducing into a muscle cell or tissue of the subject a pharmaceutical composition which comprises (a) a pharmaceutically acceptable excipient; and (b) recombinant AAV virions, wherein the recombinant AAV virions comprise an AAV vector, the AAV vector comprising a selected gene operably linked to control elements capable of directing the transcription and translation of the selected gene when present in the subject, wherein the introducing is done in vivo.
In another embodiment, the invention is directed to a method for delivering a therapeutically effective amount of a protein systemically to a mammalian subject comprising:
(a) introducing a recombinant AAV virion into a muscle cell or tissue in vitro to produce a transduced muscle cell, wherein the recombinant AAV virion comprises an AAV vector, the AAV vector comprising a selected gene operably linked to control elements capable of directing the transcription and translation of the selected gene when present in the subject; and
(b) administering to the subject a therapeutically effective amount of a composition comprising a pharmaceutically acceptable excipient and the transduced muscle cells from step (a).
In other embodiments, the invention is directed to an AAV vector comprising a gene encoding human erythropoietin (hEPO) operably linked to control elements capable of directing the in vivo transcription and translation of the gene, as well as a recombinant AAV (rAAV) virion comprising the vector.
These and other embodiments of the subject invention will readily occur to those of ordinary skill in the art in view of the disclosure herein.